Alamo Lake to be “flushed” March 12th, says Army Corps Colonel

Colonel Kirk E. Gibbs of the Army Corps of Engineers was in Parker, AZ on Monday to address the La Paz County Board of Supervisors regarding an upcoming release of water from Alamo Lake which will increase flow in the Bill Williams River downstream.

The release is necessary for maintenance of the dam, according to Gibbs, who is the Commander and District Engineer for the Los Angeles District of the Corps, responsible for 679 personnel and a $593 million annual budget.

“We’re so proud to be here,” Gibbs said as he addressed the Supervisors, making apologies for what he said was a failure to communicate as effectively as they would have wanted. He said that he wanted to listen to any concerns the Board had and build trust and communication on this and future projects affecting the local area.

He handed the presentation over to David Van Dorpe, the Deputy Engineer for the District, who went over some of the details about the upcoming release. They were joined on the phone by others in the Corp District’s team.

Alamo Dam is a remote, earth-filled, 275-foot dam which was completed in 1968, primarily to provide flood control of the Bill Williams River, which created Alamo Lake behind it in the process. It now also permits the habitat of the Bill Williams Natural Wildlife Refuge, which ends where the river flows into the Colorado River at Lake Havasu.

The upper conduit of the dam has not been inspected since 1990, according to Van Dorpe, and cannot be inspected at the current high level of the lake. The funding is available to do it now, which means flushing some of the water to reduce the elevation of the lake by around 10 feet so the inspections and possible maintenance can be carried out. In addition, sediment has built up on the ‘sill’ of the dam, which needs to be removed by flushing to expose the sill for inspection and remove hydrogen sulfide, which has a corrosive effect.

“In 1990 the inspection led to about a million dollars of repairs,” Van Dorpe told the Board, “and we’re anticipating having to do some repairs this time too, but that’s just an unknown at this point.”

The Corps maintenance divers cannot safely dive to a working depth any greater than around 110 feet, Gibbs said, which is another reason the lake elevation level must be lowered. As he was declining to get “too technical” about why a deeper dive cannot happen, Supervisor D.L. Wilson interjected to say that he is a certified diver and Gibbs then went into more detail.

Environmental Impact research has been conducted, with the greatest apparent areas of concern including the habitat of a certain kind of garter snake identified by biologists, and the recreational off-road trails which cross the Bill Williams River downstream from the dam at Planet Ranch, part of the recently-established Arizona Peace Trail.

Gibbs implied that the Corps would help to restore any off-road trails that may be washed out in the release, but said he could not commit funds beforehand. He talked about adding the Peace Trail as a stakeholder in considerations going forward.

The release is scheduled to begin on March 12th and is designed to mimic a winter storm runoff, with the majority of the release occurring over the first 3 days. The event will begin with 1000 cubic feet per second (cfs) flow, peaking at about 5000 cfs and then dropping off quickly to less than 1000 cfs and trailing off at the much reduced rate for around 20 days.

Van Dorpe said that, by the time the release reaches Planet Ranch, it would be reduced from the full 5000 cfs rate that came from the dam. The aquifer underneath Planet Ranch is currently low, so some of the water will percolate into the ground rather than continuing downstream.

Gibbs finished by saying that the dam is there to protect communities and control water flow, and that in order to do its job for the next number of decades it needs to be maintained properly and repaired where necessary. He said that it is the right time of year to minimize impacts to the environment, that the funding is finally in place and that any impacts he believes will be short-lived.

Supervisor Duce Minor asked several questions, including whether there was a possibility of dredging the sediment instead of flushing it so quickly, and releasing water at a slower rate. Gibbs and Van Dorpe said that they had considered the other options, but that they would not have the effect that was needed to meet all the criteria they were trying to meet. Minor asked about contaminants in the sediment, including the possibility of mercury from nearby mining operations. Members of the Corps team on the phone replied that there were non-detectable levels or levels below established safe thresholds.

Supervisor Irwin asked why the Corps had not taken advantage of lower lake levels in recent memory. The team replied that they had in fact submitted the request to Congress but funding did not become available until a year ago, at which time impact assessments and other red tape had still to be processed. By the time they had churned through the process, they said, the lake level had increased again.

Supervisor Minor told Parker Live that he hoped the County would be added to a ‘steering committee’ for the Bill Williams and put the County at the table with regard to future considerations.

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Watch The Nature Conservancy’s video on the Bill Williams River HERE.